Thanks for your query.Based on the facts that you have posted it appears that you have Night Emission.This is not uncommon at this age and nothing to worry about it. There is no medicine that can control this.
Following measure will help you to get sound sleep and prevent getting night emission..
1) Practice regular exercise fior 45 minutes followed by meditation
for 1/2 an hour in the morning.
2) Take high protein diet rich in vegetables and fruits and vit A,C,D,E.
3)Take anti oxidants like Almonds 5-6 everyday..
4) Avoid alcohol and smoking
The reason for getting less semen being ejaculated could be due to excessive night emission.Take some pain killer like Brufen
avilable over the counter for pain in testicles.